Long-term evolution of calcareous dinoflagellate associations since the Late Cretaceous: comparison of a high- and a low-latitude core from the Indian Ocean.

Abstract

A high and a low latitude Ocean Drilling Program core from the southern and eastern Indian Ocean, respectively, were studied to obtain a general overview of the evolution of calcareous dinoflagellate cyst associations in this region and their possible reaction to known major Cenozoic climatic changes. Despite a relatively low sample density, several shifts in calcareous dinoflagellate assemblages could be linked to periods of major climatic or environmental changes at the Cretaceous/Tertiary transition, in the early Oligocene, and in the Neogene. Correlations between changes in the climate and in the associations appear to be more distinctive at high latitudes than at low latitudes. For the first time, shifts in the stratigraphic distribution pattern of different archaeopyle types have been evaluated. The ratio between small and large archaeopyles turned out to be a possible tool for the reconstruction of long-term climatic evolution at high latitudes, with small archaeopyles correlating with warmer periods and large archaeopyles characterising cooler conditions. Altogether, 65 taxa have been distinguished of which several rare or problematic taxa, which may partly represent new species, are informally described or described using open nomenclature. Additionally, the relationship and potential synonymy of the problematic species Thoracosphaera? prolata with Calciodinellum elongatum is discussed in detail.